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Abstract:

A solid-state imaging device includes: a plurality of photoelectric
conversion units disposed on an imaging surface of a substrate; and a
plurality of inner-layer lenses that are disposed in correspondence with
each of the plurality of photoelectric conversion units on the upper side
of the photoelectric conversion units and are formed in shapes protruding
in directions toward the photoelectric conversion units, wherein each of
the plurality of inner-layer lenses is formed to have different lens
shapes in the center and in the periphery of the imaging surface.

Claims:

1. A solid-state imaging device comprising: a plurality of photoelectric
conversion units disposed on an imaging surface of a substrate; and a
plurality of inner-layer lenses that are disposed in correspondence with
each of the plurality of photoelectric conversion units on the upper side
of the photoelectric conversion units and are formed in shapes protruding
in directions toward the photoelectric conversion units, wherein each of
the plurality of inner-layer lenses is formed to have different lens
shapes in the center and in the periphery of the imaging surface, wherein
the center of each of the plurality of inner-layer lenses is disposed so
as to be shifted further to the center side of the imaging surface with
respect to the center of the photoelectric conversion unit as the
position of the each of the plurality of the inner-layer lenses disposed
on the imaging surface is more distant from the center of the imaging
surface, wherein the inner-layer lens is formed by stacking a plurality
of lens material layers, wherein each of the plurality of lens material
layers is formed such that a lower face of a first lens material layer
that is the closest to the photoelectric conversion unit of the plurality
of lens material layers has an area less than that of an upper face of a
second lens material layer that is the most distant from the
photoelectric conversion unit of the plurality of lens material layers,
and wherein a cross-section of each of the plurality of lens material
layers that is perpendicular to the imaging surface includes a tapered
portion of which a width that is defined in a direction along the imaging
surface is narrowed further in a direction toward the photoelectric
conversion unit.

2. The solid-state imaging device according to claim 1, wherein each of
the plurality of lens material layers is formed to have a refractive
index decreasing in the direction toward the photoelectric conversion
unit.

3. The solid-state imaging device according to claim 1, wherein each of
the plurality of lens material layers is formed to have a refractive
index increasing in the direction toward the photoelectric conversion
unit.

4. A solid-state imaging device comprising: a plurality of photoelectric
conversion units disposed on an imaging surface of a substrate; and a
plurality of inner-layer lenses that are disposed in correspondence with
each of the plurality of photoelectric conversion units on the upper side
of the photoelectric conversion units and are formed in shapes protruding
in directions toward the photoelectric conversion units, wherein each of
the plurality of inner-layer lenses is formed to have different lens
shapes in the center and in the periphery of the imaging surface, wherein
the center of each of the plurality of inner-layer lenses is disposed so
as to be shifted further to the center side of the imaging surface with
respect to the center of the photoelectric conversion unit as the
position of the each of the plurality of the inner-layer lenses disposed
on the imaging surface is more distant from the center of the imaging
surface, wherein the inner-layer lens is formed by stacking a plurality
of lens material layers, wherein each of the plurality of lens material
layers is formed such that a lower face of a first lens material layer
that is the closest to the photoelectric conversion unit of the plurality
of lens material layers has an area less than that of an upper face of a
second lens material layer that is the most distant from the
photoelectric conversion unit of the plurality of lens material layers,
and wherein each of the plurality of lens material layers is formed to
have a refractive index changing in the direction toward the
photoelectric conversion unit.

5. A solid-state imaging device comprising: a plurality of photoelectric
conversion units disposed on an imaging surface of a substrate; optical
waveguides disposed in correspondence with each of the plurality of
photoelectric conversion units on the upper side of the plurality of
photoelectric conversion units; and a plurality of inner-layer lenses
that are disposed in correspondence with each of the plurality of
photoelectric conversion units on the upper side of the photoelectric
conversion units and are formed in shapes protruding in directions toward
the photoelectric conversion units, wherein each of the plurality of
inner-layer lenses is formed to have different lens shapes in the center
and in the periphery of the imaging surface, and wherein each inner-layer
lens is disposed so as to be interposed between a respective one of the
optical waveguides and a respective one of the photoelectric conversion
units.

Description:

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application is a divisional of U.S. application Ser. No.
12/660,211, filed on Feb. 23, 2010, which claims priority from Japanese
Patent Application No. 2009-050771, filed on Mar. 4, 2009 in the Japanese
Patent Office, the disclosures of which are hereby incorporated by
reference herein.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The present invention relates to a solid-state imaging device, a
manufacturing method thereof, and an electronic apparatus, and more
particularly, to a solid-state imaging device in which a plurality of
photoelectric conversion units are disposed on an imaging surface of a
substrate, and a plurality of inner-layer lenses are formed in shapes
protruding in directions toward the photoelectric conversion units, a
manufacturing method thereof, and an electronic apparatus.

[0004] 2. Description of the Related Art

[0005] Electronic apparatuses such as a digital video camera and a digital
camera include solid-state imaging devices. For example, the solid-state
imaging device includes a CMOS (Complementary Metal Oxide
Semiconductor)-type image sensor and a CCD (Charge Coupled Device)-type
image sensor.

[0006] In the solid-state imaging devices, an image forming area in which
a plurality of pixels are formed is disposed on a surface of a
semiconductor substrate. In each of the plurality of pixels, a
photoelectric conversion unit that generates signal electric charges by
receiving incident light through a curved lens and performing
photoelectric conversion for the received light is disposed. For example,
a photo diode is formed as the photoelectric conversion unit.

[0007] In the solid-state imaging device, for example, an on-chip lens is
disposed on the upper side of the photoelectric conversion unit. A
configuration in which an inner-layer lens is disposed between the
photoelectric conversion unit and the on-chip lens has been proposed. The
inner-layer lens is disposed for efficiently irradiating light that is
incident through the on-chip lens onto the photoelectric conversion unit.
For example, each of a plurality of inner-layer lenses are formed to have
a downward convex structure protruding in directions toward the
photoelectric conversion unit (for example, see JP-A-2002-359363 and
JP-A-2007-324481).

SUMMARY OF THE INVENTION

[0008] In the solid-state imaging devices, the image quality of an image
that is imaged may deteriorate due to angles of main light beams, which
are received by pixels, differing in accordance with the position in the
image forming area.

[0009] In particular, in a center portion of the image forming area, the
angle of the main light beam incident through the curved lens is almost
perpendicular to the image forming area. On the other hand, in the
peripheral portion of the image forming area, the angle of the main light
beam that is incident through the curved lens is tilted with respect to
the direction perpendicular to the image forming area. Accordingly, there
are cases where the center portion of the image that is imaged becomes a
bright image, and a peripheral portion becomes a dark image, thereby
deteriorating the image quality of the image that is imaged.

[0010] In other words, there is a difference between the sensitivities of
the center portion and the peripheral portion of the image forming area,
and accordingly, there are cases where the image quality of an image that
is imaged deteriorates.

[0011] Accordingly, there is a need for providing a solid-state imaging
device capable of improving the image quality of an image that is imaged,
a manufacturing method thereof, and an electronic apparatus.

[0012] According to an embodiment of the present invention, there is
provided a solid-state imaging device including: a plurality of
photoelectric conversion units disposed on an imaging surface of a
substrate; and a plurality of inner-layer lenses that are disposed in
correspondence with each of the plurality of photoelectric conversion
units on the upper side of the photoelectric conversion units and are
formed in shapes protruding in directions toward the photoelectric
conversion units. Each of the plurality of inner-layer lenses is formed
to have different lens shapes in the center and the periphery of the
imaging surface.

[0013] According to another embodiment of the present invention, there is
provided an electronic apparatus including: a plurality of photoelectric
conversion units disposed on an imaging surface of a substrate; and a
plurality of inner-layer lenses that are disposed in correspondence with
each of the plurality of photoelectric conversion units on the upper side
of the photoelectric conversion units and are formed in shapes protruding
in directions toward the photoelectric conversion units. Each of the
plurality of inner-layer lenses is formed to have different lens shapes
in the center and the periphery of the imaging surface.

[0014] According to another embodiment of the present invention, there is
provided a method of manufacturing a solid-state imaging device. The
method includes forming a plurality of inner-layer lenses in shapes
protruding in directions toward a plurality of photoelectric conversion
units on the upper side of the plurality of photoelectric conversion
units so as to be in correspondence with each of the plurality of
photoelectric conversion units disposed on an imaging surface of a
substrate. In the forming of the plurality of inner-layer lenses, each of
the plurality of inner-layer lenses is formed to have different lens
shapes in the center and the periphery of the imaging surface.

[0015] According to an embodiment of the present invention, as described
above, by forming the lens shape of each of the plurality of inner-layer
lenses to be different in the center and in the periphery of the imaging
surface, occurrence of a difference between the sensitivities of the
center portion and the peripheral portion of the image forming area is
prevented.

[0016] According to an embodiment of the present invention, a solid-state
imaging device capable of improving the image quality of an image that is
imaged, a manufacturing method thereof, and an electronic apparatus can
be provided.

BRIEF DESCRIPTION OF THE DRAWINGS

[0017] FIG. 1 is a configuration diagram showing the configuration of a
camera 40 according to Embodiment 1 of the present invention.

[0018] FIG. 2 is a schematic plan view showing the entire configuration of
a solid-state imaging device according to Embodiment 1 of the present
invention.

[0019] FIG. 3 is a circuit diagram showing a major portion of a pixel P,
which is disposed in an image forming area PA, according to Embodiment 1
of the present invention.

[0020] FIG. 4 is a cross-sectional view representing a major portion of a
solid-state imaging device 1 according to Embodiment 1 of the present
invention.

[0021] FIG. 5 is a cross-sectional view representing a major portion of a
solid-state imaging device 1 according to Embodiment 1 of the present
invention.

[0022] FIG. 6 is a plan view showing the relationship between lens
material layers configuring an inner-layer lens 120 and a photo diode 21,
according to Embodiment 1 of the present invention.

[0023] FIG. 7 is a plan view showing the relationship between lens
material layers configuring an inner-layer lens 120 and a photo diode 21,
according to Embodiment 1 of the present invention.

[0024] FIGS. 8A and 8B are cross-sectional views representing major
portions disposed in each process of a method of manufacturing a
solid-state imaging device 1 according to Embodiment 1 of the present
invention.

[0025] FIGS. 9A and 9B are cross-sectional views representing major
portions disposed in each process of a method of manufacturing a
solid-state imaging device 1 according to Embodiment 1 of the present
invention.

[0026] FIGS. 10A and 10B are cross-sectional views representing major
portions disposed in each process of a method of manufacturing a
solid-state imaging device 1 according to Embodiment 1 of the present
invention.

[0027] FIG. 11 is a diagram showing the appearance of a main light beam
incident to a solid-state imaging device 1 according to Embodiment 1 of
the present invention.

[0028] FIG. 12 is a diagram showing the appearance of a main light beam
incident to a solid-state imaging device 1 according to Embodiment 1 of
the present invention.

[0029] FIG. 13 is a cross-sectional view representing a major portion of a
solid-state imaging device 1b according to Embodiment 2 of the present
invention.

[0030] FIG. 14 is a cross-sectional view representing a major portion of a
solid-state imaging device 1b according to Embodiment 2 of the present
invention.

[0031] FIG. 15 is a cross-sectional view representing a major portion of a
solid-state imaging device 1c according to Embodiment 3 of the present
invention.

[0032] FIG. 16 is a cross-sectional view representing a major portion of a
solid-state imaging device 1c according to Embodiment 3 of the present
invention.

[0033] FIG. 17 is a cross-sectional view representing a major portion of a
solid-state imaging device 1d according to Embodiment 4 of the present
invention.

[0034] FIG. 18 is a cross-sectional view representing a major portion of a
solid-state imaging device 1d according to Embodiment 4 of the present
invention.

[0035] FIG. 19 is a cross-sectional view representing a major portion of a
solid-state imaging device 1e according to Embodiment 5 of the present
invention.

[0036] FIG. 20 is a cross-sectional view representing a major portion of a
solid-state imaging device 1e according to Embodiment 5 of the present
invention.

[0037] FIG. 21 is a diagram showing a major portion of a solid-state
imaging device according to an embodiment of the present invention.

[0038] FIG. 22 is a diagram showing a major portion of a solid-state
imaging device according to an embodiment of the present invention.

[0039] FIG. 23 is a diagram showing a major portion of a solid-state
imaging device according to an embodiment of the present invention.

[0040] FIG. 24 is a diagram showing a major portion of a solid-state
imaging device according to an embodiment of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0041] Hereinafter, embodiments of the present invention will be described
with reference to the accompanying drawings.

[0049] FIG. 1 is a configuration diagram showing the configuration of a
camera 40 according to Embodiment 1 of the present invention.

[0050] As shown in FIG. 1, the camera 40 includes a solid-state imaging
device 1, a curved lens 42, a driving circuit 43, and a signal processing
circuit 44. Each component will be sequentially described.

[0051] The solid-state imaging device 1 generates signal electric charges
by receiving light (subject image) incident to an imaging surface PS
through the curved lens 42 and performs photoelectric conversion for the
received light. Here, the solid-state imaging device 1 is driven in
accordance with a driving signal that is output from the driving circuit
43. In particular, the solid-state imaging device 1 reads out the signal
electric charges and outputs raw data.

[0052] In this embodiment, as shown in FIG. 1, a main light beam H1 that
is output from the curved lens 42 is incident to the center portion of
the imaging surface PS at an angle to be perpendicular to the imaging
surface PS of the solid-state imaging device 1. On the other hand, a main
light beam H2 is incident to the peripheral portion of the imaging
surface PS at an angle to be tilted with respect to the direction
perpendicular to the imaging surface PS of the solid-state imaging device
1.

[0053] The curved lens 42 is arranged so as to collect incident light H
corresponding to a subject image on the imaging surface PS of the
solid-state imaging device 1.

[0054] In this embodiment, the curved lens 42 is disposed such that the
optical axis thereof is in correspondence with the center of the imaging
surface PS of the solid-state imaging device 1. Accordingly, the curved
lens 42, as represented in FIG. 1, emits the main light beam H1 to the
center portion of the imaging surface PS of the solid-state imaging
device 1 at an angle to be perpendicular to the imaging surface PS. On
the other hand, in the peripheral portion of the imaging surface PS, the
curved lens 42 emits the main light beam H2 at an angle to be tilted with
respect to the direction perpendicular to the imaging surface PS.

[0055] The driving circuit 43 outputs various driving signals to the
solid-state imaging device 1 and the signal processing circuit 44 so as
to drive the solid-state imaging device 1 and the signal processing
circuit 44.

[0056] The signal processing circuit 44 is configured so as to generate a
digital image for a subject image by performing a signal process for the
raw data that is output from the solid-state imaging device 1.

(2) Configuration of Major Portion of Solid-State Imaging Device

[0057] The entire configuration of the solid-state imaging device 1 will
be described.

[0058] FIG. 2 is a schematic plan view showing the entire configuration of
the solid-state imaging device 1 according to Embodiment 1 of the present
invention.

[0059] The solid-state imaging device 1 according to this embodiment is a
CMOS-type image sensor and includes a substrate 101 as shown in FIG. 2.
This substrate 101, for example, is a semiconductor substrate that is
formed from silicon. As shown in FIG. 2, an image forming area PA and a
peripheral area SA are disposed on the surface of the substrate 101.

[0060] The image forming area PA, as represented in FIG. 2, has a
rectangular shape, and a plurality of pixels P are disposed therein in
the directions of x and y. In other words, pixels P are aligned in a
matrix shape. In addition, the image forming area PA is disposed such
that the center thereof is in correspondence with the optical axis of the
curved lens 42 shown in FIG. 1.

[0061] This image forming area PA corresponds to the imaging surface shown
in FIG. 1. Accordingly, as described above, the main light beam (H1
represented in FIG. 1) is incident to pixels P that are disposed in the
center portion of the image forming area PA at an angle to be
perpendicular to the surface of the image forming area PA. On the other
hand, the main light beam (H2 represented in FIG. 1) is incident to
pixels P that are disposed in the peripheral portion of the image forming
area PA at an angle to be tilted with respect to the direction
perpendicular to the surface of the image forming area PA.

[0062] The peripheral area SA, as shown in FIG. 2, is disposed on the
periphery of the image forming area PA. In the peripheral area SA,
peripheral circuits that process the signal electric charges generated
for the pixels P are disposed.

[0063] In particular, as shown in FIG. 2, as the peripheral circuits, a
vertical selection circuit 13, a column circuit 14, a horizontal
selection circuit 15, a horizontal signal line 16, an output circuit 17,
and a timing generator (TG) 18 are disposed.

[0064] The vertical selection circuit 13, for example, includes a shift
register and selects the pixels P so as to be driven in units of a row.

[0065] The column circuit 14, for example, includes an S/H (sample and
hold) circuit and a CDS (Correlated Double Sampling) circuit. The column
circuit 14 performs signal processing for signals read out from the
pixels P in units of a column.

[0066] The horizontal selection circuit 15, for example, includes a shift
register and sequentially selects the signals read out from the pixels P
by the column circuit 14 so as to be output. Then, in accordance with the
selective driving performed by the horizontal selection circuit 15, the
signals read out from the pixels P are sequentially output to the output
circuit 17 through the horizontal signal line 16.

[0067] The output circuit 17, for example, includes a digital amplifier,
performs signal processing such as an amplification process for the
signals output from the horizontal selection circuit 15, and then outputs
the signals externally.

[0068] The timing generator 18 generates various timing signals and
outputs the timing signals to the vertical selection circuit 13, the
column circuit 14, and the horizontal selection circuit 15, thereby
performing driving control for each unit.

(3) Configuration of Major Portion of Pixel

[0069] FIG. 3 is a circuit diagram showing a major portion of the pixel P,
which is disposed in the image forming area PA, according to Embodiment 1
of the present invention.

[0070] The pixel P disposed in the image forming area PA, as shown in FIG.
3, includes a photo diode 21, a transmission transistor 22, an amplifier
transistor 23, an address transistor 24, and a reset transistor 25. In
other words, a photo diode 21 and a pixel transistor that reads signal
electric charges from the photo diode 21 are disposed.

[0071] In the pixel P, the photo diode 21 receives light corresponding to
a subject image and performs photoelectric conversion for the received
light, thereby generating and accumulating signal electric charges. The
photo diode 21, as shown in FIG. 3, is connected to the gate of the
amplifier transistor 23 through the transmission transistor 22. In
addition, the signal electric charges accumulated in the photo diode 21
are transmitted to a floating diffusion FD, which is connected to the
gate of the amplifier transistor 23, by the transmission transistor 22 as
an output signal.

[0072] In the pixel P, the transmission transistor 22, as shown in FIG. 3,
is disposed so as to be interposed between the photo diode 21 and the
floating diffusion FD. The transmission transistor 22 transmits the
signal electric charges accumulated in the photo diode 21 to the floating
diffusion FD as an output signal in accordance with application of a
transmission pulse from the transmission line 26 to the gate of the
transmission transistor 22.

[0073] In the pixel P, the amplifier transistor 23, as shown in FIG. 3,
has the gate connected to the floating diffusion FD and amplifies an
output signal that is output through the floating diffusion FD. Here, the
amplifier transistor 23 is connected to the vertical signal line 27
through the address transistor 24 and configures a source follower
together with a static current source I that is disposed in an area other
than the image forming area PA. The amplifier transistor 23 amplifies an
output signal output from the floating diffusion FD in accordance with
supply of an address signal to the address transistor 24.

[0074] In the pixel P, the address transistor 24, as shown in FIG. 3, has
the gate connected to the address line 28 to which the address signal is
supplied. When being supplied with the address signal, the address
transistor 24 is in the ON state and outputs the output signal amplified
by the amplifier transistor 23 as described above to the vertical signal
line 27. Then, the output signal is output to the S/H circuit and the CDS
circuit of the above-described column circuit 14 through the vertical
signal line 27.

[0075] In the pixel P, the reset transistor 25, as shown in FIG. 3, has
the gate connected to the reset line 29 to which a reset signal is
supplied and is connected so as to be interposed between the power source
Vdd and the floating diffusion FD. When a reset signal is supplied to the
gate of the reset transistor 25 from the reset line 29, the reset
transistor 25 resets the electric potential of the floating diffusion FD
to the electric potential of the power source Vdd.

[0076] The gates of the transistors 22, 24, and 25 are connected in units
of a row that is configured by a plurality of pixels aligned in the
horizontal direction x. Thus, the above-described operation for driving
the pixel is simultaneously performed for a plurality of pixels aligned
in the unit of a row. In particular, the pixels are sequentially selected
in the vertical direction in units of a horizontal line (pixel row) in
accordance with the address signal that is supplied by the
above-described vertical selection circuit 13. Then, the transistor of
each pixel is controlled in accordance with various timing signals output
from the timing generator 18. Accordingly, the output signals of each
pixel are read out by the S/H circuits and the CDS circuits of the column
circuits 14 of each pixel column through the vertical signal line 27.

(4) Detailed Configuration of Solid-State Imaging Device

[0077] The solid-state imaging device 1 according to this embodiment will
be described in detail.

[0078] FIG. 4 and FIG. 5 are cross-sectional views representing major
portions of the solid-state imaging device 1 according to Embodiment 1 of
the present invention. Here, FIG. 4 shows a cross-section of the pixel P
disposed in the center portion of the image forming area PA represented
in FIG. 2. On the other hand, FIG. 5 shows a cross-section of the pixel P
disposed in the peripheral portion of the image forming area PA
represented in FIG. 2. FIG. 5 shows a case where the right side is the
center side of the image forming area PA, and the left side is the
peripheral side of the image forming area PA.

[0079] In the image forming area PA, the pixel P is configured as
represented in FIG. 3. However, members other than the photo diode 21,
which configure the pixel P, are not shown in the figures.

[0080] As shown in FIGS. 4 and 5, in the solid-state imaging device 1, a
photo diode 21, an inner-layer lens 120, a color filter 130, and an
on-chip lens 140 are formed in correspondence with a pixel P. In
addition, here, as shown in FIGS. 4 and 5, the inner-layer lens 120 is
configured by a first inner-layer lens material layer 121, a second
inner-layer lens material layer 122, and a third inner-layer lens
material layer 123.

[0081] Each portion will be sequentially described.

[0082] The photo diode 21, as shown in FIGS. 4 and 5, is disposed on the
surface of the substrate 101. The photo diode 21 generates signal
electric charges by receiving light on a light reception surface JS and
performing photoelectric conversion for the received light. A plurality
of the photo diodes 21 are disposed on the surface of the substrate 101
in correspondence with a plurality of the pixels P shown in FIG. 2.

[0083] In addition, on the upper side of the photo diode 21, a wiring
layer 110 is disposed. In the wiring layer 110, wirings 110h electrically
connected to each element are formed inside an insulating layer 110z. The
insulating layer 110z is formed from a light-transmissive material
through which light can be transmitted. For example, the insulating layer
110z is formed from a silicon oxide film (refractive index n=1.43). In
addition, the wiring 110h is formed from a conductive material such as a
metal.

[0084] Additionally, on the upper side of the photo diode 21, as shown in
FIGS. 4 and 5, the inner-layer lens 120, the color filter 130, and the
on-chip lens 140 are disposed. Here, from the side of the light reception
surface JS, the inner-layer lens 120, the color filter 130, and the
on-chip lens 140 are sequentially disposed.

[0085] In this embodiment, as can be noticed by comparing FIGS. 4 and 5
with each other, the positions of the portions 120, 130, and 140 with
respect to the photo diode 21 differ in correspondence with the position
of the pixel P. Here, the center positions of the portions 120, 130, and
140 are disposed so as to be shifted further to the center side of the
image forming area PA with respect to the center of the light reception
surface JS of the photo diode 21 as the position of the pixel P disposed
on the image forming area PA is more distant from the center side of the
image forming area PA.

[0086] In particular, as shown in FIG. 4, in the pixel P disposed in the
center portion of the image forming area PA, the center positions of the
portions 120, 130, and 140 coincide with the center axis C of the light
reception surface JS on the upper side of the light reception surface JS.

[0087] On the other hand, as shown in FIG. 5, in the pixel P disposed in
the peripheral portion of the image forming area PA, the center positions
of the portions 120, 130, and 140 do not coincide with the center axis C
of the light reception surface JS but are shifted to one side along the
xy plane, on the upper side of the light reception surface JS. FIG. 5, as
described above, shows a case where the right side is the center side of
the image forming area PA, and the left side is the peripheral side of
the image forming area PA. Accordingly, the center positions of the
portions 120, 130, and 140 are disposed so as to be shifted to the right
side with respect to the center of the light reception surface JS.

[0088] Although not shown in the figure, in contrast to FIG. 5, in a case
where the left side is the center side of the image forming area PA, and
the right side is the peripheral side of the image forming area PA, the
center positions of the portions 120, 130, and 140 are disposed so as to
be shifted to the left side with respect to the center of the light
reception surface JS. In other words, the portions 120, 130, and 140 are
disposed such that the pitches of the portions 120, 130, and 140 are less
than the pitch of the photo diodes 21 disposed in the pixels P.

[0089] The inner-layer lens 120, as shown in FIGS. 4 and 5, are formed so
as to be positioned on the wiring layer 110 to the upper side of the
surface of the substrate 101.

[0090] In this embodiment, as can be noticed by comparing FIGS. 4 and 5
with each other, the position of the inner-layer lens 120 with respect to
the photo diode 21 differs in correspondence with the position of the
pixel P. Here, the center position of the inner-layer lens 120 is
disposed so as to be shifted further to the center side of the image
forming area PA with respect to the center of the light reception surface
JS of the photo diode 21 as the position of the pixel P disposed in the
image forming area PA is more distant from the center of the image
forming area PA. In other words, the inner-layer lenses 120 are disposed
such that the pitch of the inner-layer lenses 120 is less than the pitch
of the photo diodes 21 disposed in the pixels P.

[0091] In addition, the inner-layer lens 120 is configured to collect
light output from the color filter 130 on the surface of the substrate
101. In particular, the inner-layer lens 120 is formed such that the
center portion is thicker than the edge portion in the direction toward
the light reception surface JS of the photo diode 21.

[0092] In this embodiment, the inner-layer lens 120, as shown in FIGS. 4
and 5, is formed such that the area of the face along the light reception
surface JS of the photo diode 21 sequentially decreases in a stepped
manner in a direction from the on-chip lens 140 side toward the photo
diode 21 side.

[0093] In particular, the inner-layer lens 120 includes a first lens
material layer 121, a second lens material layer 122, and a third lens
material layer 123. The first to third lens material layers 121, 122, and
123 are sequentially stacked on the upper side of the light reception
surface JS of the photo diode 21. In the inner-layer lens 120, side faces
of the lens material layers 121, 122, and 123 are disposed in different
positions in the direction of the xy plane such that different levels are
formed on the side face along the z direction that is perpendicular to
the light reception surface JS.

[0094] The lens material layers 121, 122, and 123 are respectively formed
by using optical materials that have refractive indices higher than those
of the interlayer insulating films 111, 112, and 113 disposed on the
periphery thereof. For example, the lens material layers 121, 122, and
123 are formed by using silicon nitride (refractive index: 2.0) that is
deposited by using a plasma CVD method.

[0095] In the inner-layer lens 120, the first lens material layer 121, as
shown in FIGS. 4 and 5, is disposed in a position closest to the light
reception surface JS among the plurality of the lens material layers 121,
122, and 123.

[0096] In addition, in the inner-layer lens 120, the second lens material
layer 122, as shown in FIGS. 4 and 5, is disposed between the first lens
material layer 121 and the third lens material layer 123.

[0097] In addition, in the inner-layer lens 120, the third lens material
layer 123, as shown in FIGS. 4 and 5, is disposed in a position that is
the most distant from the light reception surface JS among the plurality
of the lens material layers 121, 122, and 123.

[0098] FIG. 6 and FIG. 7 are plan views showing the relationship between
the lens material layers 121, 122, and 123 configuring the inner-layer
lens 120 and the photo diode 21, according to Embodiment 1 of the present
invention. Here, FIG. 6, similarly to FIG. 4, represents a portion of the
pixel P disposed in the center portion of the image forming area PA
represented in FIG. 2. On the other hand, FIG. 7, similarly to FIG. 5,
represents a portion of the pixel P disposed in the peripheral portion of
the image forming area PA represented in FIG. 2. In FIGS. 6 and 7, for
convenience of illustration, the lens material layers 121, 122, and 123
configuring the inner-layer lens 120 are represented, and the photo diode
21 is denoted by a dotted line.

[0099] As shown in FIGS. 6 and 7, the planar shapes of the first to third
lens material layers 121, 122, and 123 are rectangles and are formed to
be similar to one another. In other words, the lens material layers 121,
122, and 123 are formed to have the same pattern but to have different
areas. Here, the first lens material 121 is formed to have an area larger
than that of the second lens material 122. In addition, the second lens
material layer 122 is formed to have an area larger than that of the
third lens material layer 123.

[0100] In other words, the plurality of the lens material layers 121, 122,
and 123 are formed such that the lower face of the first lens material
layer 121, which is the closest to the photo diode 21, has an area
smaller than that of the upper face of the third lens material layer 123,
which is the most distant from the photo diode 21.

[0101] In particular, as shown in FIG. 6, in the pixel P disposed in the
center portion of the image forming area PA, the center position of each
of the lens material layers 121, 122, and 123 is disposed so as to
coincide with the center C of the light reception surface JS of the photo
diode 21.

[0102] On the other hand, as shown in FIG. 7, in the pixel P disposed in
the peripheral portion of the image forming area PA, the center positions
of the lens material layers 121, 122, and 123 do not coincide with the
center C of the light reception surface JS of the photo diode 21 and are
shifted to one side along the xy plane. FIG. 7, similarly to FIG. 5,
shows a case where the right side is the center side of the image forming
area PA, and the left side is the peripheral side of the image forming
area PA. Accordingly, in this portion, the center positions of the first
to third lens material layers 121, 122, and 123 are disposed so as to be
sequentially shifted to the right side with respect to the center C of
the light reception surface JS of the photo diode 21.

[0103] The color filter 130, as shown in FIG. 4 and FIG. 5, is formed so
as to be positioned on the inner-layer lens 120 on the upper side of the
surface of the substrate 101. The color filter 130 is configured to allow
the light corresponding to the subject image to be colored and outputs
the colored light to the surface of the substrate 101. For example, the
color filter 130 is formed by coating with a coating solution containing
a coloring pigment and photoresist resin by using a coating method such
as a spin coating method so as to form a coating film and then by
patterning and processing the coating film by using lithographic
technology. Although not shown in the figure, the color filter 130 is
disposed in each pixel P as one of a green filter layer, a red filter
layer, and a blue filter layer. For example, each of the green filter
layer, the red filter layer, and the blue filter layer is disposed in a
Bayer arrangement so as to be parallel to one another.

[0104] In this embodiment, as can be noticed by comparing FIGS. 4 and 5
with each other, the position of the color filter 130 with respect to the
photo diode 21 differs in correspondence with the position of the pixel
P. Here, the center position of the color filter 130 is disposed so as to
be shifted further to the center side of the image forming area PA with
respect to the center of the light reception surface JS of the photo
diode 21 as the position of the pixel P disposed in the image forming
area PA is more distant from the center of the image forming area PA. In
other words, the color filters 130 are disposed such that the pitch of
the color filters 130 is less than the pitch of the photo diodes 21
disposed in the pixels P. In addition, the color filters 130 are disposed
such that the pitch of the color filters 130 is less than that of the
inner-layer lenses 120 disposed in the pixels P.

[0105] The on-chip lens 140, as shown in FIG. 4 and FIG. 5, is formed so
as to be positioned on the color filter 130 on the upper side of the
surface of the substrate 101. This on-chip lens 140 is configured so as
to collect incident light onto the light reception surface JS of the
photo diode 21. In particular, the on-chip lens 140 is formed such that
the center portion is thicker than the edge portion in a direction toward
the light reception surface JS of the photo diode 21.

[0106] In this embodiment, as can be noticed by comparing FIGS. 4 and 5
with each other, the position of the on-chip lens 140 with respect to the
photo diode 21 differs in correspondence with the position of the pixel
P. Here, the center position of the on-chip lens 140 is disposed so as to
be shifted further to the center side of the image forming area PA with
respect to the center of the light reception surface JS of the photo
diode 21 as the position of the pixel P disposed in the image forming
area PA is more distant from the center of the image forming area PA. In
other words, the on-chip lenses 140 are disposed such that the pitch of
the on-chip lenses 140 is less than the pitch of the photo diodes 21
disposed in the pixels P. In addition, the on-chip lenses 140 are
disposed such that the pitch of the on-chip lenses 140 is less than that
of the inner-layer lenses 120 disposed in the pixels P.

[Manufacturing Method]

[0107] Hereinafter, a major portion of a manufacturing method for
manufacturing the above-described solid-state imaging device 1 will be
described. In particular, a process for forming the inner-layer lens 120
in the solid-state imaging device 1 will be described in detail.

[0108] FIGS. 8A, 8B, 9A, 9B, 10A, and 10B are cross-sectional views
representing major portions disposed in each process of the method of
manufacturing the solid-state imaging device 1 according to Embodiment 1
of the present invention. FIGS. 8A, 9A, and 10A, similarly to FIG. 4,
show the portion of the pixel P disposed in the center portion of the
image forming area PA represented in FIG. 2. On the other hand, FIGS. 8B,
9B, and 10B, similarly to FIG. 5, show the portion of the pixel P
disposed in the peripheral portion of the image forming area PA
represented in FIG. 2.

(1) Formation of First Lens Material Layer 121

[0109] First, as represented in FIGS. 8A and 8B, the first lens material
layer 121 that configures the inner-layer lens 120 is formed.

[0110] Here, as shown in FIGS. 8A and 8B, the first lens material layer
121 is formed on the wiring layer 110.

[0111] For example, the interlayer insulating film 111 is formed on the
wiring layer 110. Then, an opening is formed in an area, which forms the
first lens material layer 121, of the interlayer insulating film 111. For
example, the interlayer insulating film 111 is formed by forming a
silicon oxide film by using a CVD method. Then, for example, the opening
is formed in the interlayer insulating film 111, for example, by using
photolithographic technology.

[0112] In this embodiment, for example, by performing an anisotropic
etching process, this formation process is performed such that the side
face of the opening is formed in a direction perpendicular to the surface
of the substrate 101.

[0113] Thereafter, by forming an optical material as a film so as to bury
the opening formed in the interlayer insulating film 111, the first lens
material layer 121 is formed. For example, after silicon nitride is
deposited by using the plasma CVD method, the surface is flattened by
performing a CMP (Chemical Mechanical Polishing) process. Accordingly,
the first lens material layer 121 is formed inside the opening.

[0114] In this embodiment, as represented in FIGS. 8A and 8B, the first
lens material layer 121 is formed such that the position of the first
lens material layer 121 with respect to the photo diode 21 differs in
correspondence with the position of the pixel P in the image forming area
PA.

[0115] In particular, this formation process is performed such that the
center position of the first lens material layer 121 is shifted further
to the center side of the image forming area PA with respect to the
center of the light reception surface JS of the photo diode 21 as the
position of the pixel P disposed in the image forming area PA is more
distant from the center of the image forming area PA. In other words, the
first lens material layer 121 is formed such that the pitch of the first
lens material layer 121 is less than the pitch of the photo diodes 21
disposed in the pixels P.

(2) Formation of Second Lens Material Layer 122

[0116] Next, as represented in FIGS. 9A and 9B, the second lens material
layer 122 that configures the inner-layer lens 120 is formed.

[0117] Here, as represented in FIGS. 9A and 9B, the second lens material
layer 122 is formed on the first lens material layer 121.

[0118] For example, after the interlayer insulating film 112 is formed on
the first lens material layer 121, an opening is formed in an area, which
forms the second lens material layer 122, of the interlayer insulating
film 112. Similarly to the case of the first lens material layer 121, the
opening is formed in the interlayer insulating film 112.

[0119] Thereafter, similarly to the case of the first lens material layer
121, the second lens material layer 122 is formed by burying an optical
material in the opening that is formed in the interlayer insulating film
112.

[0120] In this embodiment, as represented in FIGS. 9A and 9B, similarly to
the first lens material layer 121, the second lens material layer 122 is
formed such that the position of the second lens material layer 122 with
respect to the photo diode 21 differs in correspondence with the position
of the pixel P in the image forming area PA.

[0121] In particular, this formation process is performed such that the
center position of the second lens material layer 122 is shifted further
to the center side of the image forming area PA with respect to the
center of the light reception surface JS of the photo diode 21 as the
position of the pixel P disposed in the image forming area PA is more
distant from the center of the image forming area PA. Here, the second
lens material layers 122 are formed such that the pitch of the second
lens material layers 122 is less than the pitch of the first lens
material layers 121 of the pixels P.

(3) Formation of Third Lens Material Layer 123

[0122] Next, as represented in FIGS. 10A and 10B, the first lens material
layer 121 that configures the inner-layer lens 120 is formed.

[0123] Here, as represented in FIGS. 10A and 10B, the third lens material
123 is formed on the second lens material layer 122.

[0124] For example, after the interlayer insulating film 113 is formed on
the second lens material layer 122, an opening is formed in an area,
which forms the third lens material layer 123, of the interlayer
insulating film 113. Similarly to the cases of the first and second lens
material layers 121 and 122, the opening is formed in the interlayer
insulating film 113.

[0125] Thereafter, similarly to the cases of the first and second lens
material layers 121 and 122, the third lens material layer 123 is formed
by burying an optical material in the opening that is formed in the
interlayer insulating film 113.

[0126] In this embodiment, as represented in FIGS. 10A and 10B, the third
lens material layer 123 is formed such that the position of the third
lens material layer 123 with respect to the photo diode 21 differs in
correspondence with the position of the pixel P in the image forming area
PA.

[0127] In particular, this formation process is performed such that the
center positions of the second lens material layer 122 and the third lens
material layer 123 are shifted further to the center side of the image
forming area PA with respect to the center of the light reception surface
JS of the photo diode 21 as the position of the pixel P disposed in the
image forming area PA is more distant from the center of the image
forming area PA. Here, the third lens material layers 123 are formed such
that the pitch of the third lens material layers 123 is less than the
pitch of the second lens material layers 122 of the pixels P.

[0128] Thereafter, as shown in FIGS. 4 and 5, the color filter 130 and the
on-chip lens 140 are formed, and thereby the solid-state imaging device 1
is completed.

[Operation]

[0129] FIGS. 11 and 12 are diagrams showing the appearance of a main light
beam incident to the solid-state imaging device 1 according to Embodiment
1 of the present invention. Here, FIG. 11, similarly to FIG. 4,
represents a portion of the pixel P that is disposed in the center
portion of the image forming area PA represented in FIG. 2. On the other
hand, FIG. 12, similarly to FIG. 5, represents a portion of the pixel P
that is disposed in the peripheral portion of the image forming area PA
represented in FIG. 2.

[0130] As illustrated in FIG. 11, in the center portion of the image
forming area PA, the main light beam H1 is incident from the upper side
of the photo diode 21 to the light reception surface JS at an angle to be
perpendicular to the light reception surface JS. Then, the main light
beam H1 is incident to the color filter 130 through the on-chip lens 140
with the angle maintained. Thereafter, as shown in FIG. 11, the main
light beam H1 output from the color filter 130 is incident to the
inner-layer lens 120.

[0131] Here, the inner-layer lens 120 forms a lens surface Lc as denoted
by a dashed-dotted line shown in FIG. 11. In other words, the inner-layer
lens 120 is formed as a downward convex lens having the lens surface Lc
symmetrical to an axis perpendicular to the center of the light reception
surface JS. Accordingly, from the inner-layer lens 120, similarly to the
case of the on-chip lens 140, the main light beam H1 is output at an
angle perpendicular to the light reception surface JS. Then, this main
light beam H1 is incident to the light reception surface JS of the photo
diode 21 through the wiring layer 110.

[0132] On the other hand, as illustrated in FIG. 12, in the peripheral
portion of the image forming area PA, the main light beam H2 is incident
from the upper side of the photo diode 21 to the light reception surface
JS at an angle tilted with respect to the direction perpendicular to the
light reception surface JS. Then, the main light beam H2 is incident to
the color filter 130 through the on-chip lens 140 with the angle
maintained. Thereafter, as illustrated in FIG. 12, the main light beam H2
output from the color filter 130 is incident to the inner-layer lens 120.

[0133] Here, the inner-layer lens 120 forms a lens surface Ls as denoted
by a dashed-dotted line shown in FIG. 12. The inner-layer lens 120 is
formed as a downward convex lens having the lens surface Ls asymmetrical
to an axis perpendicular to the center of the light reception surface JS.
In other words, a lens that is formed by shifting an upside-down bell to
be tilted is formed. In particular, the inner-layer leans 120, as
illustrated in FIG. 12, is formed by designing the lens surface Ls so as
to refract the main light beam H2, so that the main light beam H2 is
close to the center of the light reception surface JS of the photo diode
21. Accordingly, the main light beam H2 output from the inner-layer lens
120 is incident to the light reception surface JS of the photo diode 21
through the wiring layer 110.

[Sum Up]

[0134] As described above, in this embodiment, on the upper side of a
plurality of the photo diodes 21, a plurality of the inner-layer lenses
120 are formed in a shape protruding in directions toward the photo
diodes 21. Each of the plurality of the inner-layer lenses 120 is formed
such that the shape of the lens is different in the center of the image
forming area PA and the periphery thereof. Here, each inner-layer lens
120 is disposed such that the center of the inner-layer lens 120 is
shifted further to the center side of the image forming area PA with
respect to the center of the photo diode 21 as the position of the pixel
disposed in the image forming area is more distant from the center.

[0135] Accordingly, as illustrated in FIGS. 11 and 12 described above, on
both the center and the periphery of the image forming area PA, the main
light beams H1 and H2 can be optimally incident to the photo diode 21.
Therefore, occurrence of a difference between the sensitivities of the
center and the periphery of the image forming area PA can be suppressed.

[0136] As a result, according to this embodiment, the image quality of an
image that is imaged can be improved.

[0137] In addition, in this embodiment, the inner-layer lens 120 is formed
by stacking a plurality of lens material layers 121, 122, and 123.
Accordingly, the entire shape of the inner-layer lens 120 can be designed
with a high degree of freedom, and the above-described advantages can be
acquired in an easy manner.

2. Embodiment 2

[Configuration of Device and Others]

[0138] FIG. 13 and FIG. 14 are cross-sectional views representing major
portions of the solid-state imaging device 1b according to Embodiment 2
of the present invention. Here, FIG. 13, similarly to FIG. 4, shows a
portion of the pixel P disposed in the center portion of the image
forming area PA represented in FIG. 2. On the other hand, FIG. 14,
similarly to FIG. 5, shows a portion of the pixel P disposed in the
peripheral portion of the image forming area PA represented in FIG. 2.

[0139] As shown in FIGS. 13 and 14, in this embodiment, an inner-layer
lens 120b is different from that of Embodiment 1. Except for this point,
this embodiment is the same as Embodiment 1. Thus, description of
portions common to Embodiment 1 is omitted here.

[0140] The inner-layer lens 120b, as shown in FIGS. 13 and 14, similarly
to that of Embodiment 1, includes first to third lens material layers
121b, 122b, and 123b.

[0141] The first to third lens material layers 121b, 122b, and 123b,
differently from Embodiment 1, are formed such that the side faces
thereof are tapered faces tilted with respect to the z direction that is
perpendicular to the light reception surface JS.

[0142] In particular, as shown in FIGS. 13 and 14, the side face of the
first lens material layer 121b is formed to be tilted such that the first
lens material layer 121b is narrowed in a tapered shape from the upper
side toward the lower side.

[0143] In addition, the side face of the second lens material layer 122b,
similarly to that of the first lens material layer 121b, as shown in
FIGS. 13 and 14, is formed to be tilted such that the second lens
material layer 122b is narrowed in a tapered shape from the upper side
toward the lower side. Here, the width of the lower end portion of the
second lens material layer 122b is formed to be equal to or greater than
that of the upper end portion of the first lens material layer 121b.

[0144] In addition, the side face of the third lens material layer 123b,
similarly to those of the first and second lens material layers 121b and
122b, as shown in FIGS. 13 and 14, is formed to be tilted such that the
third lens material layer 123b is narrowed in a tapered shape from the
upper side toward the lower side. Here, the width of the lower end
portion of the third lens material layer 123b is formed to be equal to or
greater than that of the upper end portion of the second lens material
layer 122b.

[0145] The lens material layers 121b, 122b, and 123b are formed by burying
lens materials in openings formed in the interlayer insulating films 111,
112, and 113. In this embodiment, each opening is formed such that the
side face of the opening is in a tapered shape having a wider width
toward the upper side in the z direction that is perpendicular to the
light reception surface JS. In particular, each opening is formed by
performing an isotropic etching process.

[Sum Up]

[0146] As described above, in this embodiment, each of the first to third
lens material layers 121b, 122b, and 123b configuring the inner-layer
lens 120b is formed such that the side face thereof is a tapered face
titled with respect to the z direction that is perpendicular to the light
reception surface JS. In other words, the inner-layer lens 120b is formed
such that the side faces of the lens material layers 121b, 122b, and 123b
are along the lens surfaces Lc and Ls shown in FIGS. 11 and 12.
Accordingly, scattering of the light incident to the inner-layer lens
120b on the lens surface can be suppressed.

[0147] As a result, according to this embodiment, occurrence of a decrease
in the sensitivity due to scattering can be prevented, and thereby the
image quality of an image that is imaged can be improved.

3. Embodiment 3

[Configuration of Device and Others]

[0148] FIG. 15 and FIG. 16 are cross-sectional views representing major
portions of a solid-state imaging device 1c according to Embodiment 3 of
the present invention. Here, FIG. 15, similarly to FIG. 4, shows a
portion of the pixel P disposed in the center portion of the image
forming area PA represented in FIG. 2. On the other hand, FIG. 16,
similarly to FIG. 5, shows a portion of the pixel P disposed in the
peripheral portion of the image forming area PA represented in FIG. 2.

[0149] As shown in FIGS. 15 and 16, in this embodiment, an inner-layer
lens 120c is different from that of Embodiment 1. Except for this point,
this embodiment is the same as Embodiment 1. Thus, description of
portions common to Embodiment 1 is omitted here.

[0150] The inner-layer lens 120c, as shown in FIGS. 15 and 16, similarly
to that of Embodiment 1, includes first to third lens material layers
121c, 122c, and 123c.

[0151] Although the first to third lens material layers 121c, 122c, and
123c have the same shapes as those of Embodiment 1, the configuration of
optical materials used for formation of the layers is different from that
of Embodiment 1.

[0152] In this embodiment, the lens material layers 121c, 122c, and 123c
are formed to include portions of which the refractive indices decrease
in a direction toward the photo diode 21. In other words, among a
plurality of the lens material layers 121c, 122c, and 123c, the first
lens material layer 121c disposed on the lowermost layer is formed by
using an optical material having the lowest refractive index. In
addition, among the plurality of the lens material layers 121c, 122c, and
123c, the third lens material layer 123c disposed on the uppermost layer
is formed by using an optical material having the highest refractive
index.

[0153] For example, the first lens material layer 121c is formed from SiON
having a refractive index of 1.7. In addition, the second lens material
layer 122c, for example, is formed from SiON having a refractive index of
1.85. The first lens material layer 121c and the second lens material
layer 122c are formed by differently adjusting the containing ratios of
[0] and [N] in using the CVD method. The third lens material layer 123c,
for example, is formed from SiN having a refractive index of 2.0.

[Sum Up]

[0154] As described above, in this embodiment, the lens material layers
121c, 122c, and 123c configuring the inner-layer lens 120c are formed to
have refractive indices decreasing in the direction toward the photo
diode 21. In such a case, occurrence of reflection at the time of output
of light from the lower surface of the inner-layer lens 120c can be
prevented. Furthermore, in a case where the refractive index of the upper
portion of the inner-layer lens 120c is high, a difference between the
refractive indices is decreased, thereby reflection from the upper end of
the lens can be suppressed.

[0155] As a result, according to this embodiment, the sensitivity can be
improved, thereby the image quality of an image that is imaged can be
improved.

4. Embodiment 4

[Configuration of Device and Others]

[0156] FIG. 17 and FIG. 18 are cross-sectional views representing major
portions of a solid-state imaging device 1d according to Embodiment 4 of
the present invention. Here, FIG. 17, similarly to FIG. 4, shows a
portion of the pixel P disposed in the center portion of the image
forming area PA represented in FIG. 2. On the other hand, FIG. 18,
similarly to FIG. 5, shows a portion of the pixel P disposed in the
peripheral portion of the image forming area PA represented in FIG. 2.

[0157] As shown in FIGS. 17 and 18, in this embodiment, an inner-layer
lens 120d is different from that of Embodiment 1. Except for this point,
this embodiment is the same as Embodiment 1. Thus, description of
portions common to Embodiment 1 is omitted here.

[0158] The inner-layer lens 120d, as shown in FIGS. 17 and 18, similarly
to that of Embodiment 1, includes first to third lens material layers
121d, 122d, and 123d.

[0159] Although the first to third lens material layers 121d, 122d, and
123d have the same shapes as those of Embodiment 1, the configuration of
optical materials used for formation of the layers is different from that
of Embodiment 1.

[0160] In this embodiment, the lens material layers 121d, 122d, and 123d
are formed to include portions of which the refractive indices increase
in a direction toward the photo diode 21. In other words, among a
plurality of the lens material layers 121d, 122d, and 123d, the first
lens material layer 121d disposed on the lowermost layer is formed by
using an optical material having the highest refractive index. In
addition, among the plurality of the lens material layers 121d, 122d, and
123d, the third lens material layer 123d disposed on the uppermost layer
is formed by using an optical material having the lowest refractive
index.

[0161] For example, the first lens material layer 121d is formed from SiN
having a refractive index of 2.0. In addition, the second lens material
layer 122d, for example, is formed from SiON having a refractive index of
1.85. The third lens material layer 123d, for example, is formed from
SiON having a refractive index of 1.7. The second lens material layer
122d and the third lens material layer 123d are formed by differently
adjusting the containing ratios of [O] and [N] in using the CVD method.

[Sum Up]

[0162] As described above, in this embodiment, the lens material layers
121d, 122d, and 123d configuring the inner-layer lens 120d are formed to
have refractive indices increasing in the direction toward the photo
diode 21. In such a case, the effective curvature of the lower surface of
the inner-layer lens 120d is increased, and accordingly, the beam bending
capability of this portion can be improved. Furthermore, in a case where
the refractive index of the upper portion of the inner-layer lens 120d is
low, a difference between the refractive indices is decreased, thereby
reflection from the upper end of the lens can be suppressed.

[0163] As a result, according to this embodiment, the sensitivity can be
improved, thereby the image quality of an image that is imaged can be
improved.

5. Embodiment 5

[Configuration of Device and Others]

[0164] FIG. 19 and FIG. 20 are cross-sectional views representing major
portions of a solid-state imaging device 1e according to Embodiment 5 of
the present invention. Here, FIG. 19, similarly to FIG. 4, shows a
portion of the pixel P disposed in the center portion of the image
forming area PA represented in FIG. 2. On the other hand, FIG. 20,
similarly to FIG. 5, shows a portion of the pixel P disposed in the
peripheral portion of the image forming area PA represented in FIG. 2.

[0165] As shown in FIGS. 19 and 20, in this embodiment, an optical
waveguide 150 is disposed further. Except for this point, this embodiment
is the same as Embodiment 1. Thus, description of portions common to
Embodiment 1 is omitted here.

[0166] The optical waveguide 150, as shown in FIGS. 19 and 20, is formed
to be positioned on the photo diode 21 on the upper side of the surface
of the substrate 101. The optical waveguide 150 is configured so as to
guide incident light to the light reception surface JS of the photo diode
21. The optical waveguide 150, as shown in FIGS. 19 and 20, is interposed
between the inner-layer lens 120 and the light reception surface JS of
the photo diode 21 and is formed so as to guide the light output from the
inner-layer lens 120 to the light reception surface JS of the photo diode
21.

[0167] In particular, on the surface of the substrate 101, as shown in
FIGS. 20 and 21, the wiring layer 110 is disposed. In the wiring layer
110, as described above, wirings 110h are disposed inside the insulating
layer 110z, and the insulating layer 110z is formed from a
light-transmissive material through which light can be transmitted. For
example, the insulating layer 110z is formed from a silicon oxide film
(refractive index n=1.43).

[0168] The optical waveguide 150, as shown in FIGS. 20 and 21, is disposed
so as to extend to the light reception surface JS of the photo diode 21
inside the wiring layer 110. The optical waveguide 150 is formed by using
an optical material that has a refractive index higher than that of the
insulating layer 110z configuring the wiring layer 110. For example, the
optical waveguide 150 is formed by using silicon nitride (refractive
index: 2.0) that is deposited by using a plasma CDV method. In other
words, the optical waveguide 150 is configured to serve as a core
portion, and the insulating layer 110z is configured to serve as a clad
portion.

[Sum Up]

[0169] As described above, in this embodiment, the optical waveguide 150
is formed so as to guide the incident light to the light reception
surface JS of the photo diode 21.

[0170] As a result, according to this embodiment, the sensitivity can be
improved, and thereby the image quality of an image that is imaged can be
improved.

6. Others

[0171] The present invention is not limited to the above-described
embodiments, and various modified examples can be employed.

[0172] In the above-described embodiments, a case where the embodiments
are applied to a CMOS image sensor has been described. However, the
present invention is not limited thereto. For example, the present
invention can be applied to a CCD image sensor.

[0173] In addition, the forming of the inner-layer lens is not limited to
that described in the above-described embodiments.

[0174] FIGS. 21 and 22 are diagrams showing major portions of a
solid-state imaging device according to such an embodiment of the present
invention. Here, FIG. 21, similarly to FIG. 5, shows a cross-section of a
portion of the pixel P that is disposed in the peripheral portion of the
image forming area PA represented in FIG. 2. FIG. 22 is a plan view
showing the relationship between lens material layers 121f, 122f, and
123f configuring an inner-layer lens 120f and the photo diode 21 in the
above-described portion.

[0175] As shown in FIG. 21, the inner-layer lens 120f, similarly to that
of Embodiment 1, includes a first lens material layer 121f, a second lens
material layer 122f, and a third lens material layer 123f. The layers are
sequentially stacked. In addition, the lens material layers 121f, 122f,
and 123f are disposed such that different levels are formed on the side
face aligned along the z direction perpendicular to the light reception
surface JS.

[0176] However, as shown in FIG. 21, the lens material layers 121f, 122f,
and 123f are disposed so as to have the curvature of the lens surface Ls
to be larger than that of Embodiment 1.

[0177] In particular, as shown in FIG. 22, gaps between the side faces
(the left side in FIG. 22), which are located on the peripheral side of
the image forming area PA, of the lens material layers 121f, 122f, and
123f are formed to be less than those of Embodiment 1.

[0178] Accordingly, the curvature of the lens surface Ls of a half lens,
which is located on the peripheral side of the image forming area PA, of
the inner-layer lens 120f may be configured to be greater than that of
Embodiment 1. When the curvature of the half lens is increased, the "beam
bending effect" that refracts the main light beam H2 can be improved
further. As in Embodiment 1, in a case where the curvature of the half
lens is less than that of the case shown in FIGS. 21 and 22, the main
light beam H2 output from the on-chip lens 140 is preferably bound in a
wide range. Accordingly, there is a margin for dimensional variations of
the inter-layer lens. Therefore, the reliability and the yield ratio of
the product can be improved.

[0179] FIGS. 23 and 24 are diagrams showing major portions of a
solid-state imaging device according to such an embodiment of the present
invention. Here, FIG. 23, similarly to FIG. 5, shows a cross-section of a
portion of the pixel P that is disposed in the peripheral portion of the
image forming area PA represented in FIG. 2. FIG. 24 is a plan view
showing the relationship between lens material layers 121g, 122g, and
123g configuring an inner-layer lens 120g and the photo diode 21 in the
above-described portion.

[0180] As shown in FIG. 23, the lens material layers 121g, 122g, and 123g
may be disposed such that the curvature of the lens surface Ls is less
than that of Embodiment 1.

[0181] In particular, as shown in FIG. 24, gaps between the side faces
(the left side in FIG. 24), which are located on the peripheral side of
the image forming area PA, of the lens material layers 121g, 122g, and
123g may be formed to be greater than those of Embodiment 1.

[0182] In other words, each of the layers may be formed to be shifted, so
that the pitch of the first lens material layers 121g of a lower layer is
longer than that of the second lens material layers 122g of a layer
located on the upper side of the lower layer, and the pitch of the third
lens material layers 123g of a layer located on a further upper side is
longer than that of the second lens material layers 122g.

[0183] By decreasing the curvature of the lens surface Ls as described
above, the lens area is widened, thereby the focus of the on-chip lens
can be loosened. In addition, the design can be performed based on the
difference between the shift amounts in an easy manner.

[0184] In addition, in the above-described embodiments, a case where the
inner-layer lens is formed by stacking three lens material layers has
been described. However, the present invention is not limited thereto.
Thus, the inner-layer lens may be formed by stacking more than 3 lens
material layers. In addition, the inner-layer lens may be formed in one
layer.

[0185] In addition, in the above-described embodiments, a case where the
present invention is applied to a camera has been described. However, the
present invention is not limited thereto. Thus, the present invention can
be applied to other electronic apparatuses such as a scanner and a copier
that include a solid-state imaging device.

[0186] The solid-state imaging devices 1, 1b, 1c, 1d, and 1e of the
above-described embodiments correspond to a solid-state imaging device
according to an embodiment of the present invention. The photo diode 21
of the above-described embodiments corresponds to a photoelectric
conversion unit according to an embodiment of the present invention. In
addition, the camera 40 of the above-described embodiments corresponds to
an electronic apparatus according to an embodiment of the present
invention. The substrate 101 of the above-described embodiments
corresponds to a substrate according to an embodiment of the present
invention. The inner-layer lenses 120, 120b, 120c, 120d, and 120e of the
above-described embodiments correspond to an inner-layer lens according
to an embodiment of the present invention. In addition, the first lens
material layers 121, 121b, 121c, 121d, and 121e of the above-described
embodiments correspond to a lens material layer or a first lens material
layer according to an embodiment of the present invention. The second
lens material layers 122, 122b, 122c, 122d, and 122e of the
above-described embodiments correspond to a lens material layer or a
first lens material layer according to an embodiment of the present
invention. In addition, the third lens material layers 123, 123b, 123c,
123d, and 123e of the above-described embodiments correspond to a lens
material layer or a second lens material layer according to an embodiment
of the present invention. The color filter 130 of the above-described
embodiments corresponds to a color filter according to an embodiment of
the present invention. In addition, the on-chip lens 140 of the
above-described embodiments corresponds to an on-chip lens according to
an embodiment of the present invention. The optical waveguide 150 of the
above-described embodiments corresponds to an optical waveguide according
to an embodiment of the present invention. In addition, the imaging
surface PS and the image forming area PA of the above-described
embodiments correspond to an imaging surface according to an embodiment
of the present invention.

[0187] It should be understood by those skilled in the art that various
modifications, combinations, sub-combinations and alterations may occur
depending on design requirements and other factors insofar as they are
within the scope of the appended claims or the equivalents thereof.

Patent applications by Hajime Nakayama, Kumamoto JP

Patent applications by SONY CORPORATION

Patent applications in class With optics peculiar to solid-state sensor

Patent applications in all subclasses With optics peculiar to solid-state sensor